This invention relates generally to a door locking system for securing a door and for allowing emergency egress.
Outwardly swinging exit doors are often found in commercial buildings. In addition to the use of outwardly opening doors by commercial establishments, residential dwellings, and in particular mobile homes, also often include outwardly opening doors. In a commercial environment, these doors are often located at the rear of the building and provide a service entrance to the establishment. Such doors are very commonly used in shopping centers as back doors to stores in the shopping center. Because these doors generally open toward a service driveway or parking area generally shielded from public view, the doors are often the target of burglars who simply chain or tie the exterior door handle to a truck or other vehicle and pull the door completely out of its door frame to obtain entry into the store. This type of burglary technique is becoming more and more common, particularly in high crime areas.
Outwardly opening doors have become popular in large part because of fire code requirements. During a fire or other emergency, an outwardly opening door affords a more efficient egress from a building than an inwardly opening door. Further, panic-type latch release mechanisms inherently operate better on an outwardly opening door than would be possible for an inwardly opening door.
Countervailing problems arise, however, when a door locking mechanism is to be provided which on one hand prevents the door from being torn from its frame by exterior pulling, and on the other hand affords a release of the door latching mechanism during an emergency situation which is in compliance with fire code standards.
Generally, fire code standards require that a door latch release mechanism be actuatable by someone pushing horizontally against the release mechanism. Panic latch releasing devices which require other than such a horizontal pushing force for actuation have often been banned by fire inspectors.
Additionally, Underwriters Laboratories, Inc., a national products testing laboratory, has standards for panic-type door locks which prohibit the use of a spring to retract a locking member of a door lock system.
Several devices have been patented which include panic-type door latch release mechanisms. For example, U.S. Pat. No. 4,961,330, issued to Evans, discloses a door locking mechanism having a panic bar door lock release mechanism. U.S. Pat. No. 4,631,528, issued to Handel, et al., and U.S. Pat. No. 4,785,286, issued to Martin, each disclose panic bar door latch release mechanisms which also include alarms for signaling when the emergency door latch release mechanism has been actuated.
Other door locking devices have been patented which attempt to increase the security of a door by providing cross bar-type structures which prevent the inward opening of an inwardly opening door. U.S. Pat. No. 4,779,910, issued to Dameron, discloses a door locking device having receptacles attached to the door jamb for receipt of a lock bar assembly. U.S. Pat. No. 4,762,350, issued to Hurtado, illustrates an electrically operated locking device primarily for inwardly opening doors of a residential dwelling. While not illustrated, the patent suggests the possibility of attaching the electrically operated device to the exterior of a door.
For outwardly opening doors, devices have been patented which attempt to tie the door into the interior door frame. U.S. Pat. No. 4,796,445, issued to Norden, discloses a door locking mechanism having rotatable locking plates which may engage the door frame. U.S. Pat. No. 4,852,291, issued to Gilbert, et al., discloses a locking device attachable to a door knob which includes telescoping bars for contacting a door frame. U.S. Pat. No. 4,856,831, granted to Roden, discloses a door lock which includes a pair of restraining bars which contact the door facings adjacent the door. Finally, U.S. Pat. No. 5,010,747, issued to Norden, discloses a locking device having arms which are engagable with plates mounted in the door frame or with retainers mounted on the door frame.
Even in view of the above-patented devices, a need still exists for a high security door locking system for an outwardly opening door having an emergency release system which is acceptable under fire codes.